Internal combustion engines comprise spark plugs for initiating combustion driving the engine piston and require a spark to ignite the compressed fuel. Conventionally an ignition coil transforms the battery's low voltage to high voltage needed to create an electric spark in the spark plugs to ignite the fuel. Common for all plugs is that they are arranged to be fitted into a well on the cylinder head piercing the wall of the combustion chamber so that the ignition terminal is brought into contact with the interior of the combustion cylinder. Direct ignition systems, where the ignition coil is mounted directly above each spark plug, are known to be advantageous since they eliminate the need of spark-plug wires and reduces leakage current as well as it makes ignition timing-control easier. Such a system is disclosed in EP0987435. These direct ignition systems are usually made up as one integrated assembly comprising both the spark plug as well as the ignition coil, whereby the spark plug is connected to the coil via an interconnecting extension body. The size (length) of the extension body in its turn is dependent on the dimensions of the motor. Spark ignited engines are sometimes designed with a vast distance (often at least 150 mm, sometimes as much as 500 mm) between the engine head and the internal combustion cylinder leading to that large spark plug constructions are needed in order for the ignition terminal to reach the cylinder. In some cases this is due to that the spark ignited engine originates from a converted diesel engine. As a diesel engine lacks spark plugs they are not designed to be serviced and the engine is therefore normally not adapted to promote easy access of any plug. Nevertheless, converting diesel engines into spark ignited engines represent a fast growing area, partly due to an increasing environmental awareness, and the ability of converting a diesel engine leads to the possibility of adapting vehicles already in use (e.g. lorry trucks, city busses etc.) to become e.g. gas-compatible.
U.S. Pat. No. 5,357,233 discloses an ignition apparatus for an internal combustion engine for providing a peaked high voltage current from an ignition coil to a spark plug through a bendable extension device including a first portion extending from the ignition coil, a second portion adapted to be connected to the spark plug and an elastic member connecting the first member to the second member so that the first member moves elastically in relation to the second member.
However, the space available under the hood is often rather limited, even quite narrow, and the lack of space may lead to difficulties when removing and/or introducing the ignition coil assembly from/into the motor. This problem leads to a need of costly design of extensions, e.g. dividing it in several parts.